1. Field of the Invention
This invention discloses a method and apparatus for utilizing fluid separation techniques for preparing a workpiece surface. Multiple fluids of differing densities and miscibilities wherein a fluid interface is present may be used to remove foreign materials on a workpiece surface.
2. Description of Related Art
During industrial workpiece fabrication, e.g., semiconductor wafer processing, wet chemical processing takes place during various standard processing steps. It is during these wet chemical processing steps that harsh chemicals (i.e. HF, H2SO4, H3PO4, HNO3, NH4OH, etc.) are used to perform various processes on the wafers such as film removal, cleaning, and/or surface conditioning. It is important for environmental and health reasons that these hazardous chemicals be removed prior to subsequent processing of the wafer. It is a common, industry recognized technique to use water as a final rinse to remove the hazardous chemicals from the wafer surface. The final step in any standard processing is to thoroughly remove all residual chemicals, including water, from the wafer surface.
Current workpiece surface preparation processes include tank processes and processes utilizing various techniques, such as megasonics, sprays, chemicals, spin, puddle, brush, etc. These techniques have been optimized singularly and in various combinations for different surface preparation applications. However, further optimization is required in order to achieve ideal particle, foreign material, etc., removal. Workpiece surface characteristics topography, prior process effects, etc., impact subsequent process effectiveness. Alternate techniques which can be used singularly or in combination with current techniques are needed that improve cleaning, surface preparation, coating and chemical removal performance. Also, there is a need for the development of more environmentally friendly processes which do not require disposal of chemicals.
It is also well known that at various stages of IC processing, the surface of the wafer is changed so as to increase or decrease the amount of exposed silicon. In the case of increasing exposed silicon, for example, as in DRAM devices utilizing deep trenches, de-ionized water (DIW) will dissolve small amounts of silicon. If the DIW is allowed to evaporate, the dissolved silica is re-deposited onto the wafer either on the surface or within structures such as deep trenches. Such silicate deposits are called watermarks. Watermarks that remain on a wafer during subsequent processing can result in defects within the ICs. Prevention of watermark formation is key to limiting defects. One method of reducing or eliminating watermark formation is to prevent the DIW from evaporating while remaining in contact with the wafer surface. To achieve this goal, it is necessary to remove the water from the surface before the wafer is exposed to the atmosphere.
Bearing in mind the problems and deficiencies of the prior art, it is therefore an object of the present invention to provide a method of performing various processes on a wafer or workpiece surface.
It is another object of the present invention to provide a method of preparing a workpiece surface which removes substantially all foreign materials and residual chemicals, including water, from the workpiece surface.
A further object of the invention is to provide a method of removing water from a workpiece surface before the workpiece is exposed to the atmosphere such that water marks are substantially eliminated from the workpiece surface.
It is yet another object of the present invention to provide an apparatus for practicing the above methods.
Still other objects and advantages of the invention will in part be obvious and will in part be apparent from the specification.